Many commentators seem surprised by France’s enthusiastic leadership of the intervention in Libya. They should not be. It arguably makes perfect sense that the French, so rigidly opposed to the overthrow of Saddam, and so reluctant to do any real fighting in Afghanistan, should be champing at the bit to send bombers to Benghazi and Qaddafi packing.

It is not simply a matter of Sarkozy opportunistically jumping into the hegemonic gap left by a feeble, ideologically torn American president. And it hardly needs to be said that it may have little to do with principle, or an urge to defend an oppressed people against a brutal tyrant.

But then France’s criteria for taking military action abroad, with or without UN approval, tend to be radically different to those of their fellow Western countries, with pride, prestige and cultural issues playing as important a role as economic self-interest or self-defense.

For instance, in the 1990s France supported the Hutu government in Rwanda and then sent troops to protect the fleeing Hutu Genocidaires, because it saw that regime as a French-speaking bulwark against the Anglophony of the invading Tutsi RPF.

When these odd – to British and American understanding – criteria are not at stake, French participation in allied interventions tends to be notably ineffective or even counter-productive, as in Afghanistan, or in Bosnia, where French officers actually warned Serb paramilitary forces of imminent NATO air strikes.

France’s conspicuous role in pushing for the current intervention in Libya no doubt had many motives, some of them conceivably quite altruistic, others less so. But two of the latter probably have much to do France’s ongoing quasi-imperial role in North Africa, and a Gallic hunger for vengeance – the latter being a phenomenon that seems particularly hard for contemporary Anglo-Saxons to appreciate.

Put simply, France is finally taking revenge for the Libyan terrorist bomb that brought down UTA Flight 722 in 1989 – long forgotten everywhere but Paris – and for Muammar Qaddafi’s repeated military attempts to establish Libyan control over Chad and other French-speaking neighbors.

Even before the current crisis, a measure of Paris’ ongoing hostility to Qaddafi was the fact that France, normally so quick to befriend the most ruthless and murderous third world dictators, especially those with oil wells, surprised its Western allies when it opposed loosening sanctions on Libya in 2003.

To understand why French air force bombers tore into a column of Libyan army vehicles on Friday, it helps to know where some of those jets are based. It was not the aircraft carrier Charles de Gaulle, but the dusty, sunbaked base in N’Djamena, Chad’s capital. The landlocked country that sits south of Libya and smack in the middle of the continent became a French colony in 1920. Though it theoretically achieved independence in 1960, if you go to Chad, there is little to indicate that it is no longer an imperial possession.

At the swimming pool of the Novotel, shaven headed Foreign Legionnaires flirt with the wives of French officials. The currency is the French-African franc, excellent croissants may be bought all over the capital, there is a daily flight from Paris. The French embassy is like a fortress, and still the largest establishment in the country. Every morning and every evening the Mirages roar off from the airport to remind the natives who is really in charge here.

Since uranium and oil were discovered here, the French have become even more reluctant to leave, as the former dictator Hissene Habre discovered to his cost. He made the mistake of entertaining overtures from American oil companies. As a result, when the inevitable coup attempt came, with one of his former generals Idriss Deby leading a column of pick-up trucks from across the border in Sudan’s Darfur province, the French ensured his defeat.

I heard the story of what happened from a former soldier in Habre’s army, while we were driving by a long line of wrecked and rusting armored vehicles. He described how he had been in a column of (French supplied) tanks and armored personnel carriers heading to meet Deby’s rebels. A French Army helicopter landed in front of the column and an officer told the Chadian general in charge that a ceasefire had been signed and that the force should return to the capital. As the column turned back in the direction it had come, more French helicopters appeared. And opened fire. With his armor thus shattered Habre was finished, and Deby took power. He too has faced rebel invasions speeding towards the capital, but so far the French have used their Mirages to give him early warning of their arrival.

For more than two decades the biggest threat to French dominance of Chad – and other Francophone countries in Central and West Africa has come from Libya. Qaddafi’s forces have battled those of Chad four times since 1978. During the first three invasions, in 1978, 1979 and the winter of 1980-81, the Libyans allied with local rebel forces, supporting their infantry with armored vehicles, artillery and air support. The third invasion resulted in the de facto partition of Chad in 1983 with Libyan forces controlling the country’s northern half, above the 16th parallel.

Fighting broke out again in 1986. But this time, in what was called the Toyota War a French-backed and equipped Chadian army was able to check the 300 tanks and Soviet-supplied helicopters of Libya’s expeditionary force. Stunned by the reverse, Qaddafi sent his elite Revolutionary Guard into action and dispatched bombers into the south of Chad. The French responded with air strikes on Libyan airbases and Chad’s army proceeded to smash the Libyan force, eventually crossing into Libya itself. The French forced a ceasefire on their Chadian clients — who were also receiving American intelligence and advice — before they could launch their own invasion of Libya proper. By then Libya lost almost a tenth of its army, with some 7,500 troops killed, and Chad’s President Hissene Habre found himself in control of the long disputed, uranium rich Aouzou strip between the two countries.

In an act of revenge similar to the Pan Am 103 bombing over Libya, Qaddafi’s secret service apparently arranged the bombing of UTA flight 772 which was scheduled to fly to Paris from Brazzaville via Ndjamena on September 19, 1989. It blew up over Niger, forty-five minutes after leaving Ndjamena, killing all 115 passengers.

A French investigation found evidence of Libyan involvement and a French court later convicted in absentia six Libyan agents, including Qaddafi’s brother-in-law and deputy head of intelligence, Abdullah Senussi. Qaddafi of course refused to extradite them to France. Their getting away with mass murder has rankled the French state ever since.

Though it is twenty-one years since that act of lese majeste and mass murder, revenge must indeed be sweet. And the French can also enjoy the rare satisfaction of knowing that unlike the British they did not betray themselves or the victims of a blown-up airliner by the kind of deal with Qaddafi that saw Abdelhasset Megrahi released.